Finishing process



Patented Apr. 18, 1933 UNITED STATES PATENT OFFICE FRANK M. CRYSTLER, or LANSING, MICHIGAN, Assrenon. T0 JOr'ms-nAmIEY 00., A

' CORPORATION OF DELAWARE FINISHING PROCESS No Drawing.

This invention relates to finishing and has for an object the provision of an improved method for finishing the surfaces of articles. More particularly, the invention contem- 5 plates the provision of an improved method for finishing the surfaces of articles with liquid coating compositions. The invention further contemplates the provision of an improved method for treating coated articles to produce lustrous and substantially imperfection-free surfaces.

It is customary to finish the surfaces of articles of manufacture such, for example, as the metal fenders and bodies of automobiles by applying thereto liquid coating compositions which form adherent films. In carrying out the heretofore customary finishing process, a surface to be finished may be provided with a prime coat or a surfacer coat or both prior to the'application of the finishing coat. After the preparation of the surface as, for example, by the application of one or more prime coats and/or one or more surfacer coats, the finishing coat may be applied by spraying the surface with a suitable liquid coating composition such, for example, as a lacquer containing nitrocellulose. The coated article may'then be subjected to a low-temperature air-drying or heat-drying operation to vaporize the solvents contained in the lacquer and produce a substantially solid and continuous, adherent film comprising the non-volatile components of the lacquer.

The resulting lacquer film usually has a rough surface occasioned by uneven flowing, uneven surface shrinkage, and by an accumulation of spray dust, dust from the air, and other foreign particles deposited from the atmosphere of the shop.

It is customary, therefore, to smooth the outer surface of the film by sanding in the presence of water or other liquid sanding medium, after which the job must be cleaned p and allowed to dry. This operation is then followed by the application of a spray mist coat of lacquer thinner to accomplish the substantial removal of sandpaper marks. Thereafter the coated surface is allowed to dry, and, after drying, it is polished through Application filed October 21, 1931. Serial No. 570,265.

the medium of appropriate polishing com.- pounds.

The heretofore customary mist coating and polishing are relatively slow and costly pro cedu'res requiring considerable time and extreme care in their execution. Furthermore,

covery that beneficial results may be obtained bysubjecting a film of finishing material to a controlled heat treatment. Thus,

for example, I havediscovered that by subjecting a film of finishing material to a controlled heat treatment, imperfections such, for example, as abrasive marks in its outer surface may be substantially obliterated, and a lustrous surface may be produced. As a result of my discovery, finishing processes may be simplified through the elimination of operations such as the mist coating and polishing operations of heretofore customary finishing processes, and surfaces of exceptional quality, smoothness and lustre may be obtained.

In carrying out av process in accordance with my invention, I apply to a suitably prepared surface a finishing film comprising one or more layers of a coating composition containing one or more substances capable of softening under the influence of heat without harmful physical alteration. For the purpose of eliminating imperfections in the outer surface of the film, the film is heated to a temperature at which the materials thereof are softened to the extent that sufficient flowing to substantially obliterate the imperfections is accomplished. Heating may be carried out in any suitable manner and in any. suitable apparatus. I prefer to heat the films with access of air to provide for beneficial oxidation and/or conversion of the materials of the film which may result in products of increased hardness upon cooling.

hardness at normal temperatures. Some of the most desirable compounds of the aforementioned types are synthetic resins of the modified phthalic anhydride glycerine type. Liquid coating compositions which are suitable for use in carrying. out the Process of the invention may also "comprise, in addition to the aforementioned type of syntheticresin, nitrocellulose, gums, solvents, diluents, etc.

which are commonly employed in forming the coating compositions at present known as lacquers.

I have successfully employed liquid coating compositions of the following types in carrying out the process of the invention.

Example I 4 Nitrocellulose 1.82% Glycerine-phthalic anhydride-linseed oil fatty acid resin 23.27% Lacquer thinner 74.00% Carbon black pigment .91% Ewample ll Nitrocellulose 1.82% Gum damar 1.86% Glycerine-phthalic anhydride-linseed oil fatty acid resin 21.41% Lacquer thinner 74.00% Carbon black pigment .91%

Example HI I Glycerine-phthalic anhydride-linseed oil fatty acid resin 17.75% Titanium dioxide pigment 6.25% Toluol 38.00% Xylol 38.00%

Ewa-mple I V Glycerine-phthalic anhydride castor oil resin 19.40% Nitrocellulose 1.30% Chrome green pigment .83% Titanium dioxide pigment 1.05% Lamp black pigment 14% Chrome yellow pigment .57%

Lacquer thinner 76.71%

The above mentioned pigments may be monly in use in the preparation of pigmented lacquers and enamels.

In coating compositions of the type described in the foregoing examples, the nitrocellulose may be of any suitable viscosity. In general, nitrocellulose of from half second to fifteen second viscosity is entirely suitable.

In carrying out a complete process of my invention for finishing metal surfaces, I may apply to the surface to be coated or finished one or more layers or films of a suitable liq: uid coating composition in the usual manner to produce a finlshing film of suitable thickness. After the finishing film has been formed, it may be subjected to a drying operation to increase its hardness sufficiently to permit the proper sanding operation. The drying operation should not be carried to the point Which will prohibit, through oxidation and/or conversion, suitable flowing out of abrasive marks in the subsequent heat treatment as is herein described. The sanding operation may be conducted with a view to eliminating only the most apparent imperfections and without attempting to avoid the formation of abrasive marks. The roughly sanded surface may then be cleaned of the slushresulting from the sanding operation, after which said surface may then be exposed to the action of heat at a temperature sufliciently high to effect flowing of material of the film to substantially obliterate the abrasive marks. In eneraLit is desirable to subject the sanded lm to the action of heat at temperatures of from 160 Fahrenheit to 250 Fahrenheit for periods of from one-half to three hours.

I claim: 7

1. The method of finishing a surface of an article of manufacture which comprises applying to the surface a film of a liquid coating composition comprising a synthetic resin, subjecting the outer surface of the film to an abrasive treatment, and heating the resulting film to obliterate abrasive marks.

2. In a process involving the application of a film of coating composition comprising a synthetic resin to a surface, and treatment of the film with an abrasive, the improvement which comprises heating the film after the abrasive treatment to produce a smooth lustrous surface.

3. The method of finishing a surface of an article of manufacture which comprises applying to the surface a film of liquid coating composition comprising a synthetic resin of the phthalic anhydride glycerine type, treating the film to increase its hardness, subjecting the outer surface of the hardened film to the action of an abrasive to produce a relatively smooth surface, and heating the resulting film to a temperature at which thephysical condition of the film is modified to the extent that abrasive marks are substantially eliminated.

'4. The method of finishing a surface of an article of manufacture which comprises applying to the surface a film of li uid coat ing composition comprising a synt etic resin, treating the film to increase its hardness, subjecting the outer surface of the hardened film to the action of an abrasive to produce a relatively smooth surface, and heating the resulting film to a temperature of about 160 F. to about 250 F. to modify the physical condition of the material thereof and effect the substantial elimination of abrasive marks.

5. The method of finishin a surface of an article of manufacture whic comprises applying to the surface a film of liquid coating composition comprising a synthetic resin of the phthalic anhydride glycerine type, treating the film to increase its hardness, subjecting the outer surface of the hardened film to the action of an abrasive to produce a relativel smooth surface, and heating the resulting lm to a temperature of about 160 F. to 250 F. to modify the physical condition of the material thereof and effect the substantial elimination of abrasive marks.

6. The method of finishing a surface of an article of manufacture which comprises applying to the surface a film of liquid coating composition comprising nitrocellulose and a synthetic resin, treating the film to increase its hardness, subjectin the outer surface of the hardened film to t e action of an abrasive to produce a relatively smooth surface,

and heating the resulting film to a temperature at which the physical condition of the film is modified to the extent that abrasive marks are substantially eliminated.

7. The method of finishing a surface of an article of manufacture which comprises applying to the surface a film of liquid coating composition comprising nitrocellulose and a synthetic resin of the phthalic anhydride glycerine type, treating the film to increase its hardness, subjectin the outer surface of the hardened film to t e action of an abrasive to produce a relatively smooth surface, and heating the resulting film to a temperature at which the physical condition of the film is modified to the extent that abrasive marks are substantially eliminated.

8. The method of finishing a surface of an article of manufacture which comprises applying to the surface a film of 1i uid coating composition comprising nitroce ulose and a synthetic resin, treating the film toincrease its hardness, subjecting the outer surface of the hardened film to the action of an abrasive to produce a relatively smooth surface, and

heating the resulting film to a temperature of about 160 F. to ahout250 F. to modify the physical condition of the material thereof and effect the substantial elimination of abrasive marks.

9. The method of finish a surface of an article of manufacture whic comprises applying to the surface a film of liquid coating comtgosition comprising nitrocellulose and a syn etic resin of thephthalic anhydrideglycerine type, treating the film' to increase its hardness, subjecting the outer surface of the hardened film to the action of an abrasive to produce a relatively smooth surface, and.

heating the resulting film to a temperature of about 160 F. to 250 F. to modify the ph sical condition of the material thereof and effect the substantial elimination of abrasive marks.

10. The method of finishing a surface which comprises applying to the surface a film of a'composition comprising one or more synthetic resins capable of softening under t e influence of heat without harmful decom osition and which upon subsequent cooling orm products of increased hardness, sub- 

